In a letter sent to congressional leaders on Tuesday, the mayors say it’s “time to test and evaluate approaches limiting” the use of the subsidies for sugar-laden beverages, in the interest of fighting obesity and related diseases.

“We need to find ways to strengthen the program and promote good nutrition while limiting the use of these resources for items with no nutritional value, like sugary drinks, that are actually harming the health of participants,” Mayor Michael Bloomberg, whose office released the letter, said in a statement. “Why should we continue supporting unhealthy purchases in the false name of nutrition assistance?”

The U.S. Department of Agriculture, which runs the food stamp program, declined to comment on Tuesday’s letter. Representatives for Republican House Speaker John Boehner and House Democratic leader Nancy Pelosi, to whom the letter was addressed, didn’t immediately respond to requests for comment.

The American Beverage Association, which has previously clashed with Bloomberg, said sugary drinks shouldn’t be singled out as a cause of obesity. It called obesity “a complex health condition that affects Americans of all income levels.”

“Targeting struggling families who rely on (food stamps’) vital safety net will not make America healthier or reduce government spending,” the association, which represents the non-alcoholic, refreshment beverage industry, said in an emailed statement.

Last year, more than 47 million Americans used the federal Supplemental Nutrition Assistance Program — SNAP — commonly referred to as food stamps.

The benefits can’t go to buy alcohol, cigarettes, hot food and some other items. Proposals to stop people from using the benefit to buy soda, candy and other items seen as unhealthy have been floated for decades; opponents have said such restrictions would be paternalistic and might discourage needy people from getting the subsidies.

Earlier this month, Bloomberg wrote to Senate Agriculture Committee members to applaud a proposal to have the USDA conduct a two-state test of limiting the use of food stamps to buy unhealthy food and drinks. The proposal wasn’t included in the version of the massive farm bill the Senate passed last week; the House is preparing to consider it this week.

The mayors’ letter also expressed concerns about the legislation’s proposed cuts in funding for food stamps and suggested providing incentives to use them for fruits and vegetables.